- Email: [email protected]
Lens hygiene and care system contamination of asymptomatic rigid gas permeable lens wearers
UTTERW EINEMANN
RTH
Clinical Article
Lens Hygiene and Care System Contamination of Asymptomatic Rigid Gas Permeable Lens Wearers Larry J. Davis,
Rigid gas permeable contact knses are associated with fewer serious adverse reactions and thereby offer an increased margin of safety despite a perceived kss strict adherence to sterile care system components. This arricle presents the kns care habits and frequency of care system contamination found in asymptomatic rigid gas permeable lens wearers. Forty-one asymptomatic rigid lens wearers presented for study. After in-office Iens insertion, the kns case and solutions were sentfor bacterial,fungal, and acanthamoeba cultures.The lenscare habitsof thesubjectswere determinedvia questionnaire.At leastI+ bacterialgrowthwas found in 34% of casesand 25% of solutions.No fungal or acanthamoeba contaminationwasfound. The dateof expiration is a poor predictor of solutionsterility. Although mostsubjects reportedwashingtheir handsbeforehandlinglenses,56% used tap water to rinse their lensesimmediatelybeforeinsertion.All storedtheir lenseswet, with 90% usingan appropriaterigid gas permeabksoakingsolution. The increasedmargin of safety offered by rigid lensesis not the result of better efficacy of care systems.Rigid kns wearers shouldbe remindedthat the useof tap water to rinselensesafter disinfectionand beforeinsertionis inappropriate. Furthermore, it shouldbe emphasizedthat the datesof expirationon solutionsshouldnot beusedasthe time to discardsolutions.Data to demonstratea reductionof care system contaminationwhen tap water is eliminatedwould provide further evidence that the use of tap water including before disinfectionshouldbe discouraged. Address reprint requests to Dr. Davis at Center for Eye Care, UM-St Louis School of Optometry, 8001 Natural Bridge Road, St. Louis, MO 63121. Accepted for publication
July 25, 1995.
ICLC, Vol. 22, September/October, 1995 0 Elsevier Science Inc. 1995 655 Avenue of the Americas, New York, NY 10010
OD,
FAA0
Keywords: Microbial contamination; contact lens care systems; rigid gas permeable contact lenses; contact lens care
Introduction Infectious keratitis continues to be an important concern for both wearers and fitters of contact lenses. Although relatively few patients experience this most seriouseffect of contact lens wear, those who do often suffer permanent vision loss. Thus, some would argue that no effort to increasethe margin of safety is too great. Various factors that may increasea patient’s chance for infection have been offered. One possibleexplanation is increasedsusceptibility of the external eye as an indirect effect of chronic hypoxia with compromised cornea and conjunctival metabolic function. I-3 Such a mechanism is particularly important for patients who use overnight lenses.Another possibility is that certain individuals have an increased susceptibility to infection through compromisedhost defenseand immune responseto microbial exposure.4 For example, it has been suggestedthat contact lensesmay facilitate adherenceof microbesto the cornea by reducing the effects of blinking, tear flow and tear lysozyme, lactoferrin, complement and other normal defense mechanisms.5-7 Lastly, the contact lensesand solutions may serveasa reservoir for microbial exposureduring contact lens wear.3*8’9A multifactorial causeseemsto be supportedby the evidence at hand. One important risk factor for increasedexposure to potential pathogens is contamination of the lensesand lens care system. Mondino et al. found that of 11 daily lens wearersand 29 extended lens wearerswho experienced a cornea1ulcer during wear, 4 and 12, respectively, had a 0692-8967/95/$10.00 SSDI 0892-8987(95)00073-4
Clinical Article contaminated case and/or were using contaminated solutions.3 Donzis et al. found that 17 (52%) of 33 cases and 7 (16%) of 45 bottles of solutions sampled from rigid lens wearers were contaminated. They went on to demonstrate that 26 (43%) of 61 cases and 9 (11%) of 81 solutions of soft contact lens wearers were contaminated.” Wilson et al. found that 20 (64%) of 31 rigid lens wearers and 34 (66%) of 5 1 soft contact lens wearers were using a contaminated case. l1 Soft lens wearers who use nonsterile sources of water are particularly susceptible to contaminated lens cases3’r1 Although the majority of soft lens users have discontinued use of nonsterile sources such as homemade saline, tap water continues to be an important component of rigid gas permeable lens care. Thus, the potential for significant care system contamination is present in the rigid lens-wearing population. Some advocate that tap water be eliminated as a component of rigid lens care, particularly before insertion.” However, it is likely that the risk for microbial keratitis in users of rigid gas permeable lenses in less than that for users of hydrogel lenses. r3-15 Clearly, the majority of patients with contaminated solutions or cases will not experience an adverse reaction. Nonetheless, one risk factor that prescribers of lenses and care systems may be able to influence is microbial exposure from the lens case and solutions. Thus, much effort continues toward a reduction of lens and lens care system contamination in order to increase the safety of contact lens wear. One important source of infection is inoculation at the time of insertion. Therefore, an estimate of the bioload at the time of insertion is one indication of the patient’s exposure to potential pathogens. This article is intended to address the following with regard to the apparent decreased risk for keratitis in rigid gas permeable lens wearers, despite more widespread use of nonsterile care systems, compared with soft lens wearers. What is the rate of lens case and solution contamination in asymptomatic rigid gas permeable lens wearers? What are the common lens care techniques practiced by the rigid gas permeable lens-wearing population? How common is the use of tap water in the care of rigid gas permeable contact lenses?
Methods Forty-one asymptomatic rigid gas permeable lens wearers out of 57 contacted who gave informed consent presented for study. Without the specific procedures to be performed or the purpose of the study being indicated, they were asked to postpone the insertion of their lenses until their arrival the morning of their initial visit. This was intended to not influence their lens care habits before their visit. They were also instructed to bring all of their lens care solutions including rewetting drops. After in-office insertion by their usual technique, they
218
ICLC, Vol. 22, September/October
1995
were instructed to close the case, leaving any residual solution inside. The cases and all solution bottles were then coded and transferred to the microbiology laboratory for study. Information regarding lens hygiene was obtained via questionnaire. Cultures: Bacterial and Fungal Cultures were taken within 4 hours of lens insertion. A sample of the remaining solution was removed aseptically from each side of the lens case via a micropipette and placed into a vial of prepared brain heart infusion broth. In the event that an insufficient volume was present, one to two drops of brain heart infusion broth was added a few minutes before the inoculum was obtained. The pipette did not come in contact with the lens case. Separate cultures were taken for the cases and solutions. One or two drops of each lens care product was combined to produce one inoculum for the solutions from each patient. The samples were incubated at 35°C in the presence of 5% C02. They were considered negative after 48 hours. Positive broth samples as determined by turbidity were subcultured onto chocolate, 5% sheep blood, and Sabhi agar. Bacterial cultures were incubated under the above conditions. The Sabhi agar was incubated at 27°C and considered negative at 3 weeks. Specific identification was determined via standard microbiologic techniques. Isolates having at least 1 + growth were considered to be potential pathogens. AcantJramoeba Acanthamoeba cultures were obtained ples onto non-nutrient agar overlaid with Escher&u cloacae. They were considered phozoites or cysts were present within 5
by streaking samEscherichia coli or negative if no trodays.
Results Microbiology: Cases All 41 subjects supplied a case for study. Fourteen (34%) of the cases were found to have at least 1 + bacterial growth. The specific organisms found are presented in Tubk 1. The age of cases (months) found to be contaminated (7.38 + 5.08 [mean + SD]; range, 0.25-17) was no different than the age of those not contaminated (7.23 + 4.79 [mean + SD]; range, 0.25-24). The risk for case contamination was marginally higher if tap water was used immediately preceding lens insertion (Tubk 2) (odds ratio = 1.67). Solutions
Thirty-two subjects supplied solutions for study. Eight (25%) of the solutions were found to have at least 1+ bacterial growth. The specific organismsfound are presented in Table 1. The number of months before the expiration of those solutionsfound to be contaminated (14.5 + 4.76 [mean + SD]; range 7-30) wasno different than the
Davis
Care System Contamination: Table 1. Organisms Cultured Solutions Examined
From 14 of 41 Cases and 8 of 32
Table 3. Risk for Case Contamination Were Contaminated
Frequency Organism Identified
Cases (N = 41)
Solutions (N = 32)
Pseudomonas aeruginosa Coagulase-negative Stuphylococcus Proteus mirabiiis PHemolytic Streptococcus Bacillus subtillis Total
10 2 1 1’ 1 15
4 3 1 8
’ Two organisms isolated. months for those not contaminated (13.33 + 6.12 [mean + SD]; range, O-41). None of the contaminated solutions
were found to be past the date of expiration. One solution not contaminated waspast the date of expiration. The risk for lens casecontamination is markedly higher if the solutions are also contaminated
(odds ratio
= 35) (Table
3).
The solutions usedwith contaminated casesare found in Table 4. Hygiene The majority of subjects (39 [95%] of 41) reported washing hands before handling their lenses.Many subjectsdid not replace their lens casein a timely fashion. The age of casesin months asreported in the questionnaire was8.6 + 6.9 (mean + SD) (range, 0.2524). All reported using an appropriate surfactant cleaner. All reported storing their lenseswet, but only 37 (90%) usedan appropriate rigid gaspermeablesoaking solution (Table 5). Most (88%) of the 26 who rinsed their lensesimmediately before insertion usedtap water (TabL 6).
Discussion Rigid gas permeable lens wearers frequently have contaminated care systems.The resultspresentedhere show a lower rate of contamination in rigid lens casesthan previous studies. One possibleexplanation for this is related to the method of collection. Sampling was designedto avoid touching the casesothat only the contents were evaluated. It is felt that contamination of the casecontents represents the most immediate risk to patients. For example, the insidesurfaceof lens caseshasbeen shown to be an excellent
Table 2. Risk for Case Contamination Water Rinse Before Insertion Group/Parameter Contaminated Not contaminated Odds ratio
if Subjects Reported Tap
Rinse in Tap H,O 9
Do Not Rinse in Tap H,O 5 13 1.67X
if Solutions
Solution Contaminated
Group/Parameter Case contaminated Case not contaminated Odds ratio
Solution Not Contaminated
7
4 20 35x
(7)(20:(l)(4)
environment for the attachment of microorganisms.Many bacteria speciesrespondto adverseconditions by secreting a thick proteinaceouscoating that enhancestheir ability to avoid dehydration and their exposure to chemicals.16This glycocalyx increaseswith the age of the case. Therefore, somebacteria may not be exposedto the disinfection components found in the solutions. Whether or not this coating is transferred to the lens surfaceduring the soakingand disinfection processis not known. However, should some of this material come in contact with the lens surface, it is unlikely to attach becauseattachment to surfacesseemsto be irreversible. 17-20The results presented here indicate that the ageof the casedoesnot necessarilyinfluence the contamination of its contents. The age of contaminated caseswasno different than the age of those that were not contaminated. It is possiblethat the rate of contamination is higher when this material is scrapedduring the culture process.These results are therefore more representative of the contamination of the contents within rigid lens cases, which may be more consistent with the contamination of the lens before insertion. Thus, at least one-third of rigid lens wearers routinely inoculate themselves with potential pathogensduring lens insertion. One possibleexplanation for the increasedsafety of rigid lensesis that rigid lensesare colonized by fewer bacteria, or perhaps, more viable organismsare found on soft lenses than on rigid lenses. The absolute numbers of organisms were not determined
by our technique.
However,
it is un-
likely that hydrogel lensesprovide the opportunity for increasednumbersof organismsto colonize the surface. Previous studies demonstrate the ability for Pseudomonas species to attach
to rigid
and soft lens materials.
Poly-
Table 4. Soaking Solutions Used With Cases Found To Be Contaminated Soaking Solutions
Case Contamination Frequency (N = 14)
Boston Boston Advance Soaclens B&L RGP Alcon Saline Flexcare B&L Saline Total
5 3 2 1 1 1 1 14
ICLC, Vol. 22, September/October
1995
219
Clinical Article Table 5. Components of
Lens
Care
Systems
Parameter
Used
Frequency
Cleaners Boston
Subjects
by (N
= 41)
24 6 6 5 41
Opticlean Opticlean II B&L RGP Total
Soaking solutions 8 8 16 5 2
Boston Boston Advance Soaclens B&L RGP Alcon Saline B&L Saline Flexcare Total
1
methylmethacrylate and rigid gaspermeablematerialsshow microbial adherence that is equal to or greater than that found for hydrogel materials.2’ Therefore, the apparent increasedsafety of rigid gaspermeablelensesis not the result of the increasedefficacy of rigid care systemscomparedwith soft. The most frequently isolated organism in this study wasPseudomonas. Thus, one would expect that many of our subjectswere repeatedly exposedto pathogens without experiencing an infection. Even though most patients do not replace their caseregularly, these resultssuggestthat the contamination of case contents is not time dependent. That is, other more immediate factors may have just as much influence on contamination as the frequency of case replacement. For example, contaminated solutions tend to result in contaminated cases.This demonstratesthe importance of reducing the frequency of solution contamination. The frequency of solution contamination is similar to that found in previous studies. The contamination of solutions was quite high (25%) and was not influenced by the date of expiration found on the bottle. Donzis et al. found that no solution open for fewer than 2 1 days asreported by patients was contaminated. r” Expiration dates are a source of potential confusion for patients. These resultsshow that practitioners should communicate the meaning of dates of expiration in pharmaceutical products. The date is intended to indicate the last day it should be opened before its useand doesnot predict sterility after opening. As the above results indicate, expiration dates are an unreliable estimate of whether or not a solution is contaminated. All
Table 6.
Rinsing
Technique
Immediately
None Tap water Alcon Saline
Before
Insertion? 15
23 2
B&L Saline
220
ICLC, Vol. 22, September/October
solutions found to be contaminated were cultured before the date of expiration found on the bottle. Thus, events after opening have a tremendous influence on the suhsequent sterility of solutions. Common methods for contamination after opening include storageat high temperatures and contact with contaminated surfacessuch as skin and countertops or floors. Practitioners should be aware of the frequency of contamination after opening and communicate such to their patients. The length of time a solution is safeto use after opening will vary, but up to 30 days seems to be an excellent conservative estimate. The number of patients who use tap water immediately before insertion is quite high (56%). This is of someconcern for two reasons.The solutions, when usedfor wetting after tap water rinsing and before insertion, will not be in contact with the lens for a time sufficient to disinfect the surface. Second, the quality of tap water is quite variable, some having significant numbers of potential pathogens. All of the subjectsin our study reside in a major metropolitan area with accessto city water. It is expected that this population is typical of the average asymptomatic rigid lens-wearing population. Clearly, tap water as a wetting agent or as a rinse after disinfection and before insertion should be avoided. In summary, the frequency of caseand solution contamination for rigid lens wearersis at least asprevalent asthat found for soft lens wearers. Thus, the decreasedrisk for microbial keratitis in rigid lens wearersis not the result of the increasedefficacy of care systems.Other factors such as better tear exchange, decreasedhypoxia, and lessdisruption of the natural host defensemechanismsappearto play a more important role. At least half of the rigid lens-wearing population usestap water for rinsing the lensesimmediately before insertion. Although this is unacceptableand should be discouraged,it further demonstrates the increased margin of safety that rigid lensesoffer. A high percentage of rigid lens wearers introduce nonsterile care system components into their eyes on a regular basiswithout an apparent increasedrisk for infection. Each of the subjectsreceived instruction regarding lens care within 1 year of their visit. All were taught that tap water may be usedafter removal and before disinfection but should not be usedbefore insertion. Obviously, this is a frequent source of confusion, as demonstrated by this study. Our data did not determine whether or not the elimination of tap water before disinfection reduces the contamination of lens cases.The data suggest, however, that those patients who rinse their lenseswith tap water before insertion are more likely to have a contaminated lens case. It would be desirableto have data to support that the elimination of all tap water including before disinfection reduces the frequency of contamination and offers a larger margin of safety for rigid lens wearers.
1
1995
Acknowledgment Thanks to Marilyn C. Kincaid, MD, and Earline Gurley, BSMT (ASCP), who assistedwith cultures.
Care System Contamination:
References 12. 1. Chalupa E, Swarbrick HA, Holden BA, Sjostrand J: Severe comeal infections associated with contact lens wear. Ophthalmology 1987;94:17-22. 2. Donnenfeld E, Cohen E, Arensten J, Genvert GI, Laibson PR: Changing trends in contact lens associated cornea1 ulcers. CLAO J 1986;12:145-149. 3. Mondino B, Weissman BA, Farb MD, Pettit TH: Cornea1 ulcers associated with daily-wear and extended-wear contact lenses. Am J Ophthalmol 1986;102:58-65. 4. Fleiszig SMJ, Fletcher EL, Lowe R: Microbiology of contact lens care. In: Bennett ES, Weissman BA (Ed.): Clinical Contact Lens Practice. Philadelphia, JB Lippincott, 1991. 5. Rydberg M: Bacteriology in continuous wearing of soft contact lenses. Cont Intraoc Lens Med J 1975;1:15C-152. 6. Selinger DS, Selinger RC, Reed WP: Resistance to infection of the external eye: The role of tears. Surv Ophthalmol 1979; 24~33-38. 7. Bruce AS, Brennan NA: Cornea1 pathophysiology with contact lens wear. Surv Ophthalmol 1990;35:25-58. 8. Adams CP, Cohen EJ, Laibson PR, Galentine P, Arentsen JJ: Cornea1 ulcers in patients with cosmetic extended-wear contact lenses. Am J Ophthalmol 1983;96:705-709. 9. Galentine PG, Cohen EJ, Laibson PR, Adams CP, Michaud R, Arentsen JJ: Cornea1 ulcers associated with contact lens wear. Arch Ophthalmol 1984;102:891-894. 10. Donzis PB, Mondino BJ, Weissman BA, Bruckner DA: Microbial contamination of contact lens care systems. Am .I Obhthulmol 1987;104:325-333. 11. Wilson LA, Sawant AD, Simmons RB, Aheam IX? Micro-
13.
14.
15.
16.
17. 18.
19.
20.
21.
Davis
bial contamination of contact lens storage cases and solutions. Am J Opthulmol 1990;110:193-198. Cohen EJ: Tap water and hard contact lenses. CLAO J 1989; 15:164. Dart JKG, Stapleton F, Minassian D: Contact lenses and other risk factors in microbial keratitis. Lancet 1991;338:65& 653. Buehler PO, Schein OD, Stamler JF, Verdier DD, Katz J: The increased risk of ulcerative keratitis among disposable soft contact lens users. Arch Ophthalmol 1992;110:15551558. Matthews TD, Frazer DG: Risks of keratitis and patterns of use with disposable contact lenses. Arch Ophthalmol 1992; 110:1559-1562. Caroline PJ, Campbell RC: Strategies of microbial cell survival in contact lens cases. Contact Lens Forum 1990;15:2736. Bell GI: Models for the specific adhesion of cells to cells. Science 1978;200:618-627. Duran ]A, Refojo MF, Gipson IK, Kenyon KR: Pseudomonas attachment to new hydrogel contact lenses. Arch Ophthalmol 1987;105:106109. Baum J, Panjwani N: Adherence of pseudomonas to soft contact lenses and cornea: Mechanisms and prophylaxis. In: Cavanagh HD (Ed.). The cornea: Transactions of the World Congress on the Cornea. III. New York, Raven Press, 1988; pp. 301-307. Fleiszig S, Efron N: Pathogenesis of contact lens induced bacterial cornea1 ulcers-a review and an hypothesis. Clin Exp Optom 1988;71:147-157. Dart lK, Badenoch PR: Bacterial adherence to contact lenses: CIAO J 1986;12:22@-224
J. Davis, OD, is an Assistant Professorof Optometry at UM-St. Louis School of Optometry and Adjunct Assistant Professorof Ophthalmology at St. Louis University School of Medicine. He is a 1987 graduate of Indiana University School of Optometry, and completed a residency in Cornea and Contact Lensesat UM-St. Louis, School of Optometry. He is a Fellow of the American Academy of Optometry. He served as director of the Contact Lens Service at St. Louis University Department of Ophthalmology from 1988 to 1993.
Larry
ICE,
Vol. 22, September/October
1995
221
RTH
Clinical Article
Lens Hygiene and Care System Contamination of Asymptomatic Rigid Gas Permeable Lens Wearers Larry J. Davis,
Rigid gas permeable contact knses are associated with fewer serious adverse reactions and thereby offer an increased margin of safety despite a perceived kss strict adherence to sterile care system components. This arricle presents the kns care habits and frequency of care system contamination found in asymptomatic rigid gas permeable lens wearers. Forty-one asymptomatic rigid lens wearers presented for study. After in-office Iens insertion, the kns case and solutions were sentfor bacterial,fungal, and acanthamoeba cultures.The lenscare habitsof thesubjectswere determinedvia questionnaire.At leastI+ bacterialgrowthwas found in 34% of casesand 25% of solutions.No fungal or acanthamoeba contaminationwasfound. The dateof expiration is a poor predictor of solutionsterility. Although mostsubjects reportedwashingtheir handsbeforehandlinglenses,56% used tap water to rinse their lensesimmediatelybeforeinsertion.All storedtheir lenseswet, with 90% usingan appropriaterigid gas permeabksoakingsolution. The increasedmargin of safety offered by rigid lensesis not the result of better efficacy of care systems.Rigid kns wearers shouldbe remindedthat the useof tap water to rinselensesafter disinfectionand beforeinsertionis inappropriate. Furthermore, it shouldbe emphasizedthat the datesof expirationon solutionsshouldnot beusedasthe time to discardsolutions.Data to demonstratea reductionof care system contaminationwhen tap water is eliminatedwould provide further evidence that the use of tap water including before disinfectionshouldbe discouraged. Address reprint requests to Dr. Davis at Center for Eye Care, UM-St Louis School of Optometry, 8001 Natural Bridge Road, St. Louis, MO 63121. Accepted for publication
July 25, 1995.
ICLC, Vol. 22, September/October, 1995 0 Elsevier Science Inc. 1995 655 Avenue of the Americas, New York, NY 10010
OD,
FAA0
Keywords: Microbial contamination; contact lens care systems; rigid gas permeable contact lenses; contact lens care
Introduction Infectious keratitis continues to be an important concern for both wearers and fitters of contact lenses. Although relatively few patients experience this most seriouseffect of contact lens wear, those who do often suffer permanent vision loss. Thus, some would argue that no effort to increasethe margin of safety is too great. Various factors that may increasea patient’s chance for infection have been offered. One possibleexplanation is increasedsusceptibility of the external eye as an indirect effect of chronic hypoxia with compromised cornea and conjunctival metabolic function. I-3 Such a mechanism is particularly important for patients who use overnight lenses.Another possibility is that certain individuals have an increased susceptibility to infection through compromisedhost defenseand immune responseto microbial exposure.4 For example, it has been suggestedthat contact lensesmay facilitate adherenceof microbesto the cornea by reducing the effects of blinking, tear flow and tear lysozyme, lactoferrin, complement and other normal defense mechanisms.5-7 Lastly, the contact lensesand solutions may serveasa reservoir for microbial exposureduring contact lens wear.3*8’9A multifactorial causeseemsto be supportedby the evidence at hand. One important risk factor for increasedexposure to potential pathogens is contamination of the lensesand lens care system. Mondino et al. found that of 11 daily lens wearersand 29 extended lens wearerswho experienced a cornea1ulcer during wear, 4 and 12, respectively, had a 0692-8967/95/$10.00 SSDI 0892-8987(95)00073-4
Clinical Article contaminated case and/or were using contaminated solutions.3 Donzis et al. found that 17 (52%) of 33 cases and 7 (16%) of 45 bottles of solutions sampled from rigid lens wearers were contaminated. They went on to demonstrate that 26 (43%) of 61 cases and 9 (11%) of 81 solutions of soft contact lens wearers were contaminated.” Wilson et al. found that 20 (64%) of 31 rigid lens wearers and 34 (66%) of 5 1 soft contact lens wearers were using a contaminated case. l1 Soft lens wearers who use nonsterile sources of water are particularly susceptible to contaminated lens cases3’r1 Although the majority of soft lens users have discontinued use of nonsterile sources such as homemade saline, tap water continues to be an important component of rigid gas permeable lens care. Thus, the potential for significant care system contamination is present in the rigid lens-wearing population. Some advocate that tap water be eliminated as a component of rigid lens care, particularly before insertion.” However, it is likely that the risk for microbial keratitis in users of rigid gas permeable lenses in less than that for users of hydrogel lenses. r3-15 Clearly, the majority of patients with contaminated solutions or cases will not experience an adverse reaction. Nonetheless, one risk factor that prescribers of lenses and care systems may be able to influence is microbial exposure from the lens case and solutions. Thus, much effort continues toward a reduction of lens and lens care system contamination in order to increase the safety of contact lens wear. One important source of infection is inoculation at the time of insertion. Therefore, an estimate of the bioload at the time of insertion is one indication of the patient’s exposure to potential pathogens. This article is intended to address the following with regard to the apparent decreased risk for keratitis in rigid gas permeable lens wearers, despite more widespread use of nonsterile care systems, compared with soft lens wearers. What is the rate of lens case and solution contamination in asymptomatic rigid gas permeable lens wearers? What are the common lens care techniques practiced by the rigid gas permeable lens-wearing population? How common is the use of tap water in the care of rigid gas permeable contact lenses?
Methods Forty-one asymptomatic rigid gas permeable lens wearers out of 57 contacted who gave informed consent presented for study. Without the specific procedures to be performed or the purpose of the study being indicated, they were asked to postpone the insertion of their lenses until their arrival the morning of their initial visit. This was intended to not influence their lens care habits before their visit. They were also instructed to bring all of their lens care solutions including rewetting drops. After in-office insertion by their usual technique, they
218
ICLC, Vol. 22, September/October
1995
were instructed to close the case, leaving any residual solution inside. The cases and all solution bottles were then coded and transferred to the microbiology laboratory for study. Information regarding lens hygiene was obtained via questionnaire. Cultures: Bacterial and Fungal Cultures were taken within 4 hours of lens insertion. A sample of the remaining solution was removed aseptically from each side of the lens case via a micropipette and placed into a vial of prepared brain heart infusion broth. In the event that an insufficient volume was present, one to two drops of brain heart infusion broth was added a few minutes before the inoculum was obtained. The pipette did not come in contact with the lens case. Separate cultures were taken for the cases and solutions. One or two drops of each lens care product was combined to produce one inoculum for the solutions from each patient. The samples were incubated at 35°C in the presence of 5% C02. They were considered negative after 48 hours. Positive broth samples as determined by turbidity were subcultured onto chocolate, 5% sheep blood, and Sabhi agar. Bacterial cultures were incubated under the above conditions. The Sabhi agar was incubated at 27°C and considered negative at 3 weeks. Specific identification was determined via standard microbiologic techniques. Isolates having at least 1 + growth were considered to be potential pathogens. AcantJramoeba Acanthamoeba cultures were obtained ples onto non-nutrient agar overlaid with Escher&u cloacae. They were considered phozoites or cysts were present within 5
by streaking samEscherichia coli or negative if no trodays.
Results Microbiology: Cases All 41 subjects supplied a case for study. Fourteen (34%) of the cases were found to have at least 1 + bacterial growth. The specific organisms found are presented in Tubk 1. The age of cases (months) found to be contaminated (7.38 + 5.08 [mean + SD]; range, 0.25-17) was no different than the age of those not contaminated (7.23 + 4.79 [mean + SD]; range, 0.25-24). The risk for case contamination was marginally higher if tap water was used immediately preceding lens insertion (Tubk 2) (odds ratio = 1.67). Solutions
Thirty-two subjects supplied solutions for study. Eight (25%) of the solutions were found to have at least 1+ bacterial growth. The specific organismsfound are presented in Table 1. The number of months before the expiration of those solutionsfound to be contaminated (14.5 + 4.76 [mean + SD]; range 7-30) wasno different than the
Davis
Care System Contamination: Table 1. Organisms Cultured Solutions Examined
From 14 of 41 Cases and 8 of 32
Table 3. Risk for Case Contamination Were Contaminated
Frequency Organism Identified
Cases (N = 41)
Solutions (N = 32)
Pseudomonas aeruginosa Coagulase-negative Stuphylococcus Proteus mirabiiis PHemolytic Streptococcus Bacillus subtillis Total
10 2 1 1’ 1 15
4 3 1 8
’ Two organisms isolated. months for those not contaminated (13.33 + 6.12 [mean + SD]; range, O-41). None of the contaminated solutions
were found to be past the date of expiration. One solution not contaminated waspast the date of expiration. The risk for lens casecontamination is markedly higher if the solutions are also contaminated
(odds ratio
= 35) (Table
3).
The solutions usedwith contaminated casesare found in Table 4. Hygiene The majority of subjects (39 [95%] of 41) reported washing hands before handling their lenses.Many subjectsdid not replace their lens casein a timely fashion. The age of casesin months asreported in the questionnaire was8.6 + 6.9 (mean + SD) (range, 0.2524). All reported using an appropriate surfactant cleaner. All reported storing their lenseswet, but only 37 (90%) usedan appropriate rigid gaspermeablesoaking solution (Table 5). Most (88%) of the 26 who rinsed their lensesimmediately before insertion usedtap water (TabL 6).
Discussion Rigid gas permeable lens wearers frequently have contaminated care systems.The resultspresentedhere show a lower rate of contamination in rigid lens casesthan previous studies. One possibleexplanation for this is related to the method of collection. Sampling was designedto avoid touching the casesothat only the contents were evaluated. It is felt that contamination of the casecontents represents the most immediate risk to patients. For example, the insidesurfaceof lens caseshasbeen shown to be an excellent
Table 2. Risk for Case Contamination Water Rinse Before Insertion Group/Parameter Contaminated Not contaminated Odds ratio
if Subjects Reported Tap
Rinse in Tap H,O 9
Do Not Rinse in Tap H,O 5 13 1.67X
if Solutions
Solution Contaminated
Group/Parameter Case contaminated Case not contaminated Odds ratio
Solution Not Contaminated
7
4 20 35x
(7)(20:(l)(4)
environment for the attachment of microorganisms.Many bacteria speciesrespondto adverseconditions by secreting a thick proteinaceouscoating that enhancestheir ability to avoid dehydration and their exposure to chemicals.16This glycocalyx increaseswith the age of the case. Therefore, somebacteria may not be exposedto the disinfection components found in the solutions. Whether or not this coating is transferred to the lens surfaceduring the soakingand disinfection processis not known. However, should some of this material come in contact with the lens surface, it is unlikely to attach becauseattachment to surfacesseemsto be irreversible. 17-20The results presented here indicate that the ageof the casedoesnot necessarilyinfluence the contamination of its contents. The age of contaminated caseswasno different than the age of those that were not contaminated. It is possiblethat the rate of contamination is higher when this material is scrapedduring the culture process.These results are therefore more representative of the contamination of the contents within rigid lens cases, which may be more consistent with the contamination of the lens before insertion. Thus, at least one-third of rigid lens wearers routinely inoculate themselves with potential pathogensduring lens insertion. One possibleexplanation for the increasedsafety of rigid lensesis that rigid lensesare colonized by fewer bacteria, or perhaps, more viable organismsare found on soft lenses than on rigid lenses. The absolute numbers of organisms were not determined
by our technique.
However,
it is un-
likely that hydrogel lensesprovide the opportunity for increasednumbersof organismsto colonize the surface. Previous studies demonstrate the ability for Pseudomonas species to attach
to rigid
and soft lens materials.
Poly-
Table 4. Soaking Solutions Used With Cases Found To Be Contaminated Soaking Solutions
Case Contamination Frequency (N = 14)
Boston Boston Advance Soaclens B&L RGP Alcon Saline Flexcare B&L Saline Total
5 3 2 1 1 1 1 14
ICLC, Vol. 22, September/October
1995
219
Clinical Article Table 5. Components of
Lens
Care
Systems
Parameter
Used
Frequency
Cleaners Boston
Subjects
by (N
= 41)
24 6 6 5 41
Opticlean Opticlean II B&L RGP Total
Soaking solutions 8 8 16 5 2
Boston Boston Advance Soaclens B&L RGP Alcon Saline B&L Saline Flexcare Total
1
methylmethacrylate and rigid gaspermeablematerialsshow microbial adherence that is equal to or greater than that found for hydrogel materials.2’ Therefore, the apparent increasedsafety of rigid gaspermeablelensesis not the result of the increasedefficacy of rigid care systemscomparedwith soft. The most frequently isolated organism in this study wasPseudomonas. Thus, one would expect that many of our subjectswere repeatedly exposedto pathogens without experiencing an infection. Even though most patients do not replace their caseregularly, these resultssuggestthat the contamination of case contents is not time dependent. That is, other more immediate factors may have just as much influence on contamination as the frequency of case replacement. For example, contaminated solutions tend to result in contaminated cases.This demonstratesthe importance of reducing the frequency of solution contamination. The frequency of solution contamination is similar to that found in previous studies. The contamination of solutions was quite high (25%) and was not influenced by the date of expiration found on the bottle. Donzis et al. found that no solution open for fewer than 2 1 days asreported by patients was contaminated. r” Expiration dates are a source of potential confusion for patients. These resultsshow that practitioners should communicate the meaning of dates of expiration in pharmaceutical products. The date is intended to indicate the last day it should be opened before its useand doesnot predict sterility after opening. As the above results indicate, expiration dates are an unreliable estimate of whether or not a solution is contaminated. All
Table 6.
Rinsing
Technique
Immediately
None Tap water Alcon Saline
Before
Insertion? 15
23 2
B&L Saline
220
ICLC, Vol. 22, September/October
solutions found to be contaminated were cultured before the date of expiration found on the bottle. Thus, events after opening have a tremendous influence on the suhsequent sterility of solutions. Common methods for contamination after opening include storageat high temperatures and contact with contaminated surfacessuch as skin and countertops or floors. Practitioners should be aware of the frequency of contamination after opening and communicate such to their patients. The length of time a solution is safeto use after opening will vary, but up to 30 days seems to be an excellent conservative estimate. The number of patients who use tap water immediately before insertion is quite high (56%). This is of someconcern for two reasons.The solutions, when usedfor wetting after tap water rinsing and before insertion, will not be in contact with the lens for a time sufficient to disinfect the surface. Second, the quality of tap water is quite variable, some having significant numbers of potential pathogens. All of the subjectsin our study reside in a major metropolitan area with accessto city water. It is expected that this population is typical of the average asymptomatic rigid lens-wearing population. Clearly, tap water as a wetting agent or as a rinse after disinfection and before insertion should be avoided. In summary, the frequency of caseand solution contamination for rigid lens wearersis at least asprevalent asthat found for soft lens wearers. Thus, the decreasedrisk for microbial keratitis in rigid lens wearersis not the result of the increasedefficacy of care systems.Other factors such as better tear exchange, decreasedhypoxia, and lessdisruption of the natural host defensemechanismsappearto play a more important role. At least half of the rigid lens-wearing population usestap water for rinsing the lensesimmediately before insertion. Although this is unacceptableand should be discouraged,it further demonstrates the increased margin of safety that rigid lensesoffer. A high percentage of rigid lens wearers introduce nonsterile care system components into their eyes on a regular basiswithout an apparent increasedrisk for infection. Each of the subjectsreceived instruction regarding lens care within 1 year of their visit. All were taught that tap water may be usedafter removal and before disinfection but should not be usedbefore insertion. Obviously, this is a frequent source of confusion, as demonstrated by this study. Our data did not determine whether or not the elimination of tap water before disinfection reduces the contamination of lens cases.The data suggest, however, that those patients who rinse their lenseswith tap water before insertion are more likely to have a contaminated lens case. It would be desirableto have data to support that the elimination of all tap water including before disinfection reduces the frequency of contamination and offers a larger margin of safety for rigid lens wearers.
1
1995
Acknowledgment Thanks to Marilyn C. Kincaid, MD, and Earline Gurley, BSMT (ASCP), who assistedwith cultures.
Care System Contamination:
References 12. 1. Chalupa E, Swarbrick HA, Holden BA, Sjostrand J: Severe comeal infections associated with contact lens wear. Ophthalmology 1987;94:17-22. 2. Donnenfeld E, Cohen E, Arensten J, Genvert GI, Laibson PR: Changing trends in contact lens associated cornea1 ulcers. CLAO J 1986;12:145-149. 3. Mondino B, Weissman BA, Farb MD, Pettit TH: Cornea1 ulcers associated with daily-wear and extended-wear contact lenses. Am J Ophthalmol 1986;102:58-65. 4. Fleiszig SMJ, Fletcher EL, Lowe R: Microbiology of contact lens care. In: Bennett ES, Weissman BA (Ed.): Clinical Contact Lens Practice. Philadelphia, JB Lippincott, 1991. 5. Rydberg M: Bacteriology in continuous wearing of soft contact lenses. Cont Intraoc Lens Med J 1975;1:15C-152. 6. Selinger DS, Selinger RC, Reed WP: Resistance to infection of the external eye: The role of tears. Surv Ophthalmol 1979; 24~33-38. 7. Bruce AS, Brennan NA: Cornea1 pathophysiology with contact lens wear. Surv Ophthalmol 1990;35:25-58. 8. Adams CP, Cohen EJ, Laibson PR, Galentine P, Arentsen JJ: Cornea1 ulcers in patients with cosmetic extended-wear contact lenses. Am J Ophthalmol 1983;96:705-709. 9. Galentine PG, Cohen EJ, Laibson PR, Adams CP, Michaud R, Arentsen JJ: Cornea1 ulcers associated with contact lens wear. Arch Ophthalmol 1984;102:891-894. 10. Donzis PB, Mondino BJ, Weissman BA, Bruckner DA: Microbial contamination of contact lens care systems. Am .I Obhthulmol 1987;104:325-333. 11. Wilson LA, Sawant AD, Simmons RB, Aheam IX? Micro-
13.
14.
15.
16.
17. 18.
19.
20.
21.
Davis
bial contamination of contact lens storage cases and solutions. Am J Opthulmol 1990;110:193-198. Cohen EJ: Tap water and hard contact lenses. CLAO J 1989; 15:164. Dart JKG, Stapleton F, Minassian D: Contact lenses and other risk factors in microbial keratitis. Lancet 1991;338:65& 653. Buehler PO, Schein OD, Stamler JF, Verdier DD, Katz J: The increased risk of ulcerative keratitis among disposable soft contact lens users. Arch Ophthalmol 1992;110:15551558. Matthews TD, Frazer DG: Risks of keratitis and patterns of use with disposable contact lenses. Arch Ophthalmol 1992; 110:1559-1562. Caroline PJ, Campbell RC: Strategies of microbial cell survival in contact lens cases. Contact Lens Forum 1990;15:2736. Bell GI: Models for the specific adhesion of cells to cells. Science 1978;200:618-627. Duran ]A, Refojo MF, Gipson IK, Kenyon KR: Pseudomonas attachment to new hydrogel contact lenses. Arch Ophthalmol 1987;105:106109. Baum J, Panjwani N: Adherence of pseudomonas to soft contact lenses and cornea: Mechanisms and prophylaxis. In: Cavanagh HD (Ed.). The cornea: Transactions of the World Congress on the Cornea. III. New York, Raven Press, 1988; pp. 301-307. Fleiszig S, Efron N: Pathogenesis of contact lens induced bacterial cornea1 ulcers-a review and an hypothesis. Clin Exp Optom 1988;71:147-157. Dart lK, Badenoch PR: Bacterial adherence to contact lenses: CIAO J 1986;12:22@-224
J. Davis, OD, is an Assistant Professorof Optometry at UM-St. Louis School of Optometry and Adjunct Assistant Professorof Ophthalmology at St. Louis University School of Medicine. He is a 1987 graduate of Indiana University School of Optometry, and completed a residency in Cornea and Contact Lensesat UM-St. Louis, School of Optometry. He is a Fellow of the American Academy of Optometry. He served as director of the Contact Lens Service at St. Louis University Department of Ophthalmology from 1988 to 1993.
Larry
ICE,
Vol. 22, September/October
1995
221